Automatic alternating current arc welding apparatus



Feb. 12, 1935. w. R. HARDING 1,991,091

AUTOMATIC ALTERNATING CURRENT ARC WELDING APPARATUS Filed April 24, 1954 W1TNESSES I INVENTOR Z MY/fam/E Hera 07g.-

Patented Feb. 12, 1935 PATENT OFFICE AUTOMATIC ALTEBNATING CURRENT ABCWELDING APPARATUS William It. Harding, Wilkinsburg, Pa., assignor toWestinghouse Electric & Manufacturing Company, East Pittsburgh, Pa., acorporation of Pennsylvania Application April 24, 1934, Serial No.722,063

8 Claims.

My invention relates, generally to electric welding and it hasparticular relation to automatic alternating current arc weldingsystems.

The object of my invention, generally stated, is to provide an automaticalternating current arc welding system which shall be simple and emcientin operation and which may be readily and economically manufactured andinstalled.

The principal object of my invention is to provide for feeding a weldingelectrode to a welding are at such a rate as to maintain the arc voltagesubstantially constant.

An important object of my invention is to provide for operating analternating current motor to feed a welding electrode to maintain thevoltage of an alternating current arc substantially constant.

Another important object of my invention is to provide for maintainingthe proper phase relationship between the armature and field fluxes 01an alternating current motor employed to feed a welding electrode tomaintain the voltage or a welding arc substantially constant.

Other objects of my invention will in part be obvious and in part appearhereinafter.

My invention accordingly is disclosed in the embodiment hereoi shown inthe accompanying drawing'and comprises the features of construction,combination of elements and arrangementof parts which will'be'exemplified in the con struction hereinafter set forth and the scope ofthe application of-which will be indicated in the appended claims.

For a more complete understanding of the nature and scope of myinvention, reference may be had to the following detailed descriptiontaken in connection with the accompanying drawing, in which the singlefigure diagrammatically represents a concrete embodiment o! myinvention. Referring now particularly to the single figure of thedrawing, the reference character 1 designates, generally, a weldingtransformer having a primary winding 2 connected to be energized from asource of alternating current 3. The transformer l is provided with asecondary winding 4 which is connected, as illustrated, to maintain awelding are 5 betweena welding electrode 6 and work 7 on which a weldingoperation is to be performed. It will be understood that the weldingelectrode 6 may be either of the metallic or carbon type.

In order to feed the welding electrode 6 an alternating current motor,shown generally at 8, is provided and disposed, as shown, to drive afeed roller 9 which is disposed in engagement with the welding electrode6. An idler roller 10, mounted on the opposite side 01 the weldingelectrode 6 from the feed roller 9, is provided to cooperate with thelatter. The motor 8 is provided with an armature winding 11 and a fieldwinding 12 which are connected to be energized in a manner which will beset forth in detail hereinafter.

'It is desirable to so control the operation of the feed motor athat itwill cause the welding electrode 6 to be fed downwardly to engage thework '1 and to strike the are 5. When the are 5 is struck, it isdesirable to reverse the feeding of the welding electrode 6 and towithdraw it so that the are 5 will be at the desired length which maybemeasured by the arc voltage. In order to maintain the arc voltagesubstantially constant, the motor 8 is then caused to feed the weldingelectrode 6 at such a rate and in accordance with the arcvoltage as tomaintain the latter substantially constant.

Generally stated, the control of the motor 8 is cheated by altering therelationship existing between the fluxes generated by the armaturewinding 11 and the field winding 12. This may be accomplished byreversing the direction of cur-'- rent flow through the field winding 12while maintaining the direction of current flow through the armaturewinding in the same direction.

With a view to eifecting the desired control of the flux generatedby'the field winding 12, a Wheatstone bridge circuit, shown generally at13, is provided, three legs of which comprise impedances shown generallyat 14, 15 and 16. The fourth legor' branch of the Wheatstone bridgecircuit 13 comprises the'circuit including the are 5 which is maintainedbetween the welding electrode 6 and the work '7. g

As illustrated, each of the impedances 14, 15 and ifivcomprisesrespectively inductors 14a, 15a and 16a and resistors 14b, 15b and 16b.It will be observed that the, resistor 16b is adjustable for a purposewhich will be set forth hereinafter. The corners or terminals of theWheatstone bridge may be designated, respectively, by the numerals 1'7,l8, l9 and 20, as illustrated.

It will be observed that one terminal oi the armature winding ll of themotor 8 is connected to the terminal 18 of the Wheatstone bridge circult13, and that the remaining terminal 0! the armature winding 11 and theterminal 20 oi the Wheatstone bridge circuit, or the combination, areconnected to be energized from the source of alternating current 3 whichis a substantially constant potential source. It will also be observedthat the field winding 12 is connected across the Wheatstone bridgecircuit 13 to the terminals 17 and 19,

In operation, assuming that the welding elec trode 6 is out ofengagement with the work 7, a maximum or open circuit voltage will existthere between. This voltage as applied across the terminals 17 and 20 ofthe Wheats'mne bridge 13 will be higher than the voltage existingbetween the terminals 19 and 20. As a result, current will flow throughthe field winding 12 in such direction as to cause the motor 8 to feedthe welding electrode 6 downwardly until it engages the work 7.

When the welding electrode 6 engages the work 7, the voltage acrossterminals 17 and 20 of the'wheatstone bridge 13 falls to substantiallyzero. The voltage across terminals 19 and 20, which remainssubstantially constant will then cause the current to flow through thefield winding 12 in a direction opposite to that in which it flowedpreviously and the motor 8 will thereupon be caused to reverse towithdraw the welding electrode 6 thereby increasing the length of theare 5 and consequently, the voltage between the terminals 17 and 20.When the voltage existing between terminals 17 and 20 is equal to thevoltage existing between terminals 19 and 20, it will be readilyunderstood that no current will flow through the field winding 12. As aresult, the motor 8 will stop and will withdraw the welding electrode 6no further.

Due to the fact that the welding are 5 causes the welding electrode 6 tobe melted away, the voltage between the terminals 1? and. 2c of theWheatstone bridge circuit 13 will be increased and current will becaused to flow through the field winding 20 in such a direction as tocause the motor 8 to again feed the welding electrode 6 downwardly. Thewelding electrmie 6 will then be fed downwardly by the motor 8 at a ratewhich will maintain the voltage across the arc ii a sub-- stantiallyconstant value.

In the event that it is desired to operate at dii ierent arc voltages,the adiustable resistor too may be adjusted to either increase ordecrease the resistance between the terminals 19 and 2c of theWheatstone bridge i3, thereby eiiecting a corresponding increase ordecrease the vol igc oi the are 5 which will he maintained by the motorii in feeding the welding electrode it It will be understood that thevarious imped ances 14, 15 and 16 will be so adjusted as to niaintainthe proper phase relationship between the flux generated by theai'iiiature winding 11 and the field winding 1.2, It will he observed tit the armature winding 11 is comieoted in or. circuit relation with thefield winding 12: througlii the Wheatstone bridge circuit 1.; so that itmore readily possible to maintain the desired phase relationship in thefluxes.

It will be apparent to those skilled in the art that the connections oithe armature winding 11 and the field winding 12 may be interchangedwith no fundamental change in the operation oi the system. It will alsobe understood u transformer may be interposed ii itwt the Wheatstonebridge circuit 13 and the c cluding the welding arc ii." such a comhhiapparatus is thought desirable.

Since certain further changes may be made in the above construction anddifferent embtuli ments of the invention may be made without de partingfrom the scope thereof, it intended, that all matter contained in theabove dcscript-l Ur tut one of the windings of said i'eed time or shownin the accompanying drawing shall be interpreted as illustrative and notin a limiting sense.

I claim as my invention:

1. An automatic arc welding system comprls- 5 ing, in combination, asource of current connected to maintain an are between a weldingelectrode and work on which a welding operation is to be peri'ormed, afeed motor provided with field and armature windings having drivingconnection with said electrode for feeding it, and a Wheatstone bridgecircuit including said arc as one branch connected in series circuitrelation with motor, the other winding of said feed motor beingconnected across said Wheatstone bridge circuit.

2. An automatic arc welding system comprising in combination, a sourceof welding current connected to maintain an are between a weldingelectrode and work on which a welding opera- 20 tion is to be performed,a iced motor including field and armature windings and having driving'connection with said electrode for lffltdiiig i a Vi/lieu tone bridgecircuit including the are as one branch connected in series circuitrclotion with one of said windings of said iced motor, and a source ofsubstantially constant voltage, the series connected bridge circuit andmotor winding being connected to said source of voltage and the other inr winding being con nected corms said ridge circuit,

3. outou ttic tiou to oci'ii'i field and immature condo 'on with so" Iconnected iii-1 go coi'inccted to said source and the other winding oirent connected to n welding electrode 11 titled with field on drivin areit Willi-- i in motor w Mung-u, and a it til mating coro u coiiitioctedge circuit in mg be connecte to said source KlE *Cllliifiiil; voltage"d the other me being connected it said bridge controlling the operationof said motor up; said electrode tillillllinliiiill the voltage .i areat i 'tuiit. an actor rent, trane oriner connected to he a w' iiileldding haul 1g diiv g connection with ip'ifififitfm't tor it; ling. it tomaintainthearmandawheatatonebridgecircuit having three branchescomprising impedance! and the rcurth branch formed by said are, saidbridge circuit being connected in series circuit relation with one ofsaid motor windings and the combination connected to said source ofalternating current, the other motor winding being connected across saidbridge circuit for con trolling the operation of said motor in feeding.

said electrode to maintain the voltage of said arc substantiallyconstant.

6. An automatic arc welding system comprising, in combination, a sourceof alternating current, a transformer having a primary winding connectedto be energized from said source of alternating current and a secondarywinding connected to maintain an are between a welding electrode andwork on which a welding Operation is to be performed, a feed motorprovided with field and armature windings having driving connection withsaid electrode ior feeding it to maintain the arc, and a Wheatstonebridge circuit having three branches comprising impedances and thefourth branch formed by said are, said bridge circuit being connected inseries circuit relation with the armature winding of said motor and thecombination connected to said source of alternating current, the fieldwinding of said motor being connected across said bridge circuit forcontrolling the operation of said motor in ieeding said electrode tomaintain the voltage of said arc substantially constant.

'1. An automatic arc welding system compris ing, in combination, asource of welding current connectedto maintain an are between a weldingelectrode and work. a feed motor proage, said bridge circuit beingconnected in series circuit relation with one of said motor windings andthe combination connected to said source of voltage, the other motorwinding being connected across said bridge circuit for controlling theoperation of said motor in feeding said electrode to maintain thevoltage of said are substantially constant.

8. An automatic arc welding system comprising, in combination, a sourceof welding current connected to maintain an are between a weldingelectrode and work, a feed motor provided with field and armaturewindings having driving connection with said" electrode for feeding itto maintain the arc, a Wheatstone bridge circuit having three branchescomprising impedances and the fourth branch formed by said arc, and asource of substantially constant voltage, said bridge circuit beingconnected in series circuit relation with the armature winding of saidmotor and the combination connected to said source of voltage, the fieldwinding of said motor being connected across said bridge circuit forcontrolling the operation of said motor in feeding said electrode tomaintain the voltage of said are substantially constant,

WILLIAM R. HARDING.

